December 1, 1916.] 



THE INDIA RUBBER WORLD 



127 



Proceedings of the "Rubber Section" — Continued. 



Two important addresses delivered before the Rubber Section of the American Chemical Society during the September, 

 1916, Convention U'ere printed in the October issue, followed by three other interesting papers in the November issue. 

 Below is given a summary of the symposium on "The Accelerated Life Test of Rubber Goods," in which some 20 rubber 

 chemists participated, including Dr. 'w. C. Ceer, C. R. Boggs, D. W. Whipple, J. B. Tattle, P. L. Wormclcy, Dr. L. E. 

 Weber and Messrs. Postmontier, Clark, Barrier, Thompson, Pierce, Kimley, Burns, Potts and Saunders. 



DR. L. E. WEBER presided, and in introducing Dr. Gear, 

 stated that he was probably the first man in this country 

 to put an accelerated age test to practical use. He em- 

 phasized the paramount importance of aging tests for manufac- 

 tured goods despite the fact that chemists have been carrying out 

 accelerated tests in various ways and with various results, so 

 that whereas some consider them of inestimable value, others 

 claim that no satisfactory accelerated test has yet been devised. 

 Dr. Geer then spoke briefly regarding his methods, as follows : 



The first work done in the laboratories of The B. F. Goodrich 

 Co. on accelerated age tests was in the fall of 1907, at which time 

 a suggestion came to us from Dr. Van der Linde, of the Gutta 

 Percha & Rubber Co., at Toronto, who used a very fast aging 



pound the tensile curve of which falls off more rapidly than that 

 of another compound of the same type will deteriorate more 

 slowly on standing over a period of months or years under room 

 conditions. We now have the results of ordinary aging tests 

 plotted in months, in comparison with the accelerated aging tests 

 plotted in days for the same compound, cured under the same 

 conditions, and we find them quite similar in form. 



But compounds differ. There are so many factors entering into 

 compounds that a great deal of judgment is required. Several 

 t}-pes of tensile curves have been stated. 



The method is of no great value in the lower classes of com- 

 pounds. It is more valuable in the higher classes ; for instance, 

 in such types and compounds as fire hose and articles of that 

 kind. It is a service test designed for compounds that are stored 

 a.': part of their service. The accelerated aging test is not reliable 

 when applied to compounds designed for special purposes and it 



W. C. Geer. 



D. W. Whipple. 



C. R. BoGGS, 



test. He performed it upon three small pieces of rubber. The 

 samples to be tested were put in an air bath and heated at about 

 140 degrees C. for a period of 1. 2 and 3 hours, taken out and 

 e,\amined for cracking, hardening or to ascertain whether it was 

 becoming soft. This method was not parallel with actual aging 

 in any particular and we came to the following: Into an oven, 

 heated air was blown at a temperature of 160 degrees F., the 

 chief care being to add hot fresh air during the desired time. A 

 number of samples 3/32 of an inch in thickness were previously 

 cut and put into this air bath. The air was then started circu- 

 lating and the test was continued for a period of two weeks, tak- 

 ing out three samples each day. These were allowed to stand 

 for 24 hours until they reached a state of equilibrium, after which 

 they were tested for tensile strength and elongation. The data 

 were plotted in curve form and gave us a time-decay curve of 

 the compound. It is worth while to emphasize the point that we 

 consider this purely a practical, not an ultimate test. It was 

 always run in comparison with a standard compound : that is, 

 at least two sets of samples were tested at the same time. By 

 comparing, then, the curve of a compound the age of which we 

 knew, and the curve of a compound the age of which we did not 

 know, we could tell whether the article would age properly in 

 service. 



We have run many thousands of these curves and this method 

 of determining the aging test is reliable, although it undoubtedly 

 can be greatly improved. We find, for instance, that a com- 



is very questionable whether it is at all valuable as a specification 

 test to be applied by the consumer. Its primary value lies in the 

 fact that it is an aid to the compounder in the manufacturing 

 plant to permit him to study the aging of compounds the mate- 

 rials of which he knows. It might be used by consumers as 

 mentioned above for compounds such as fire hose where storage 

 under ordinary conditions plays a large part and where it is neces- 

 sary that the compound be soft and flexible throughout its life. 



These remarks I realize are very incomplete, for it has been 

 impossible for me to find time to write a paper on this subject. 

 My primary purpose in speaking before this meeting is to sug- 

 gest for your earnest consideration the study of accelertited 

 aging tests in order that it may be possible for the rubber manu- 

 facturer to give to the consumer compositions of certain age and 

 thus tend to eliminate from the rubber business the perishable 

 features of rubber compounds. 



In answer to questions, during the discussion which followed. 

 Dr. Geer stated that his tests were carried out under air con- 

 ditions and in the dark. His samples were put in a drawer 

 separated by a sheet of cardboard, and the temperatures given 

 were varying to a certain extent, although the temperature of 

 the room did not ordinarily exceed 95 degrees in summer and 

 never became very cold in winter, as there was continuous heat. 

 Thus the aging tests ran parallel with a reasonable varying de- 



